System and method for controlling storage of electronic files

ABSTRACT

A storage control system comprising overlap retrieval means for retrieving overlap files, which are stored in at least one storage area of a plurality of storage areas, and which overlap one another, and storage controlling means for storing data of at least one overlapped part of the retrieved overlap files in a storage area having reliability that is greater than that of the storage area in which the data of this overlapped part is stored. A large number of files are stored in a plurality of storage areas, and overlap retrieval means retrieves overlap files from among a number of files, which is smaller than the number of stored files.

CROSS-REFERENCE TO PRIOR APPLICATION

This application relates to and claims priority from Japanese PatentApplication No. 2005-163801, filed on Jun. 3, 2005, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to technology for controlling the storageof electronic files.

2. Description of the Related Art

For example, in today's information society, the number of files instorage is increasing on a daily basis, and this is a source of concernfor people who utilize storage (for example, information processingsystem users and storage administrators). Among these files, there arenumerous files that are not really necessary (for example, backups ofold files, or files that have been copied and left as-is without muchthought being given to them). Since deleting these unnecessary filesincreases free storage capacity, the technology disclosed in JapanesePatent Laid-open Publication No. 7-319897, for example, is known astechnology for controlling the storage of electronic files. In thistechnology, for example, the degree of conformance of a first and asecond file stored on a storage medium is acquired, and from thisacquired degree of conformance a determination is made as to whether ornot the first file and the second file are similar, and when, as aresult, they are determined to be similar, one of them, either the firstfile or the second file, is deleted from the above-mentioned storagemedium.

In the above-mentioned Japanese Patent Laid-open Publication No.7-319897, when a first and a second file are determined to be similar,one of them, either the first file or the second file, is deleted. Thissaves storage capacity that would have been consumed. However, inJapanese Patent Laid-open Publication No. 7-319897, there is noparticular criterion for determining which of the files, the first fileor the second file, is saved. For this reason, there is no way oflowering the risk of the saved file being lost.

Further, in the above-mentioned Japanese Patent Laid-open PublicationNo. 7-319897, a determination of similarity is carried out by comparingall files using the brute force method. However, for example, when alarge number of files are stored, since the scope of the searchconstitutes all of these numerous files, finding files that are similarto one another takes a long time.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to lower the risk of afile being lost.

A further object of the present invention is to make it possible toshorten the time it takes to detect files, which are either completelyor partially overlapped, to at least less than the time required fordetection using the brute force method.

Other objects of the present invention will become clear from thefollowing explanation.

A storage control system according to a first aspect of the presentinvention comprises overlap retrieval means for retrieving overlapfiles, which are stored in at least one storage area of a plurality ofstorage areas, and which overlap one another; and storage controllingmeans for storing data of at least one overlapped part of theabove-mentioned retrieved overlap files in a storage area havingreliability that is greater than that of the storage area in which thedata of this overlapped part is stored.

In one embodiment, a large number of files is stored in theabove-mentioned plurality of storage areas. The above-mentioned overlapretrieval means can retrieve the above-mentioned overlap files fromamong a number of files, which is smaller than the number ofabove-mentioned stored files. Here, “large number of” can be taken tomean more than “a plurality of”.

In one embodiment, a storage control system can comprise means forreading a file from at least one storage area; and file marking means,which, each time a file is read out, marks the file that has been readout, and controls the number of marked files to a number less than theabove-mentioned number of stored files. The above-mentioned overlapretrieval means can retrieve a file that is an overlap of a certain filefrom among a plurality of marked files.

In one embodiment, the above-mentioned overlap retrieval means candetermine, sequentially from the most recently marked file, whether ornot a file from among the above-mentioned marked plurality of filesoverlaps the above-mentioned certain file.

In one embodiment, the above-mentioned overlap retrieval means canretrieve a file, which overlaps the above-mentioned certain file, fromamong one or more files for which either the entire or a part of thefilename, and/or the file size matches that of the above-mentionedcertain file, when the above-mentioned file, which are overlapped, arenot found among the above-mentioned marked plurality of files.

In one embodiment, a reliability storage region can also be provided.This storage region is capable of storing reliability informationrelated to the reliability of each storage areas. When two files arecompletely matched one another, the above-mentioned storage controlmeans can make a determination based on the above-mentioned reliabilityinformation as to which file resides in the storage area with thehighest reliability, and can release the location of the file thatresides in the storage area with low reliability, and leave the filethat is in the high-reliability storage area.

In one embodiment, a reliability storage region, which is capable ofstoring reliability information related to the respective reliability ofa plurality of storage areas, can also be provided. When old and updatefiles partially overlap one another, the above-mentioned storage controlmeans, based on the above-mentioned reliability information, can storethe update file in a storage area that is more reliable than the storagearea in which the old file is stored, generate a difference file of theold and update files, store the above-mentioned difference file in atleast one storage area, and release the location where at least the dataof the overlapped parts of the above-mentioned old file reside. Thedifference file referred to here, for example, can be used as adifference File Based on a New File (difference File(BNF)), which willbe explained hereinbelow.

In one embodiment, log file updating means for writing informationrelated to the above-mentioned retrieved overlap files into a prescribedlog file can also be provided. The above-mentioned overlap retrievalmeans can retrieve the above-mentioned overlap files based oninformation stored in the above-mentioned log file.

In one embodiment, the above-mentioned storage control system can alsobe connected to another storage control system so as to enablecommunications. The above-mentioned storage control means, bytransferring all the files in a primary storage area of theabove-mentioned plurality of storage areas to the above-mentionedanother storage control system, can copy the above-mentioned all of thefiles to a secondary storage area accessible by the above-mentionedseparate storage control system, and thereafter, when a certain file ofthe above-mentioned primary storage area is updated, can transfer atleast the metadata of the update file to the above-mentioned separatestorage control system.

More specifically, for example, storage control means of theabove-mentioned storage control system can transfer an update fileitself and file metadata to a separate storage control system. In thiscase, storage control means of the separate storage control systemreceives an update file and metadata of that file, and, in accordancewith the received file-metadata, can write the received update file tothe above-mentioned secondary storage area.

Further, for example, separate storage control means of theabove-mentioned storage control system can, on the basis of an old fileand an update file, generate a difference file Based on an Old File(difference File(BOF)), which will be explained hereinbelow, forgenerating an update file based on an old file, and, in addition, cantransfer the difference file(BOF) to the above-mentioned another storagecontrol system. In this case, the above-mentioned another storagecontrol means receives the difference file (BOF), generates an updatefile on the basis of the received difference file(BOF) and the old fileresiding in the above-mentioned secondary storage area, and can storethe generated update file in the above-mentioned secondary storage areain accordance with the received file-metadata.

In one embodiment, the above-mentioned storage control system can beconnected, so as to enable communications, to a backup device foracquiring a file stored in at least one storage area, and backing it upin a backup storage area. The above-mentioned storage control system canfurther comprise means for hiding the above-mentioned retrieved overlapfile from the above-mentioned backup device.

In one embodiment, the above-mentioned storage control means cangenerate a metadata aggregate file in which is recorded a large numberof file-metadata corresponding to a respective large number of filesstored in the above-mentioned plurality of storage areas, store theabove-mentioned generated metadata aggregate file in at least onestorage area, and send the above-mentioned stored metadata aggregatefile to the above-mentioned backup device, thereby enabling restorationbased on the file-metadata recorded in the above-mentioned metadataaggregate file.

In one embodiment, the above-mentioned storage control means can createa physical address image file (raw-image file) of at least one physicaladdress image from among the above-mentioned plurality of storage areas,and send the above-mentioned created raw-image file to theabove-mentioned backup device.

In one embodiment, the above-mentioned storage control means can back upat least one overlapped part of the above-mentioned retrieved overlapfiles in a storage area that has higher reliability than the storagearea in which this overlapped part data is stored.

In one embodiment, when a backup source file is updated after theabove-mentioned backup, the above-mentioned storage control means canreflect the results of this update in the backup destination.

In one embodiment, a storage control system can comprise a thresholdvalue storage region for storing a threshold value for the number offiles, which are overlapped, and means for prompting a user to deleteunnecessary overlap files when the number of the above-mentionedretrieved overlap files becomes greater than the above-mentionedthreshold value.

A storage control system according to a second aspect of the presentinvention comprises overlap retrieval means for retrieving overlapfiles, which overlap one another, from among a number of files that isless than the number of files stored in a plurality of storage areas;and controlling means for carrying out prescribed processing for theabove-mentioned retrieved overlap files.

The above-mentioned means can be realized using components, such ashardware, computer programs or a combination thereof. Computer programscan either be downloaded via a communications network, or read fromstorage media, such as CD-ROM or DVD (Digital Versatile Disk). Further,the processing for implementing the respective means can either becarried out using one component, or a plurality of components.

A storage control system according to a third aspect of the presentinvention comprises at least one storage region (for example, memory),and at least one processor. The above-mentioned at least one processorread files from at least one storage device of the plurality of storagedevices in which a large number of files are stored, and each time afile is read, marks the read file on the above-mentioned storage region,and controls the number of marked files to a number that is less thanthe number of files stored in the above-mentioned plurality of storagedevices, retrieves a file that is an overlap of a certain file fromamong the marked plurality of files, and stores data of at least oneoverlapped part of the above-mentioned retrieved overlap files in astorage device that has reliability, which is greater than that of thestorage device in which the data of this overlapped part is stored.

A processor, for example, can be a microprocessor, which reads in andexecutes a computer program.

A storage device can either be a physical storage device (for example, ahard disk), or a logical storage device (for example, a logical unit ora logical volume).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one portion of an information processing system having aNAS controller to which a storage control system related to a firstembodiment of the present invention is applied;

FIG. 2 shows one portion of the remainder of the information processingsystem related to the first embodiment of the present invention;

FIG. 3A shows an example configuration of a storage management table 51;

FIG. 3B shows an example configuration of a reliability comparison table55;

FIG. 4 shows an example configuration of a file comparison table 53, andone example of an information processing flow that utilizes this table53;

FIG. 5A is a schematic diagram of processing for copying a file A infolder X to folder Y;

FIG. 5B is a conceptual view of one example of releasing an overlap dataarea;

FIG. 6A is a conceptual view of another example of releasing an overlapdata area;

FIG. 6B is a conceptual view of yet another example of releasing anoverlap data area;

FIG. 7 shows one example of a file read process flow when an overlapdata area is not released;

FIG. 8 shows one example of a file write process flow when an overlapdata area is not released;

FIG. 9 shows one example of a file read process flow when an overlapdata area is released;

FIG. 10 shows a portion of an example of a file write process flow whenan overlap data area is released;

FIG. 11 shows another portion of an example of a file write process flowwhen an overlap data area is released;

FIG. 12 shows yet another portion of an example of a file write processflow when an overlap data area is released;

FIG. 13A shows an example of a display based on an overlap file list;

FIG. 13B shows an example of the deletion of an update file based on anoverlap file list;

FIG. 13C shows an example of processing when specifying an overlap filebased on an overlap file list;

FIG. 14 shows an overview of an information processing system related toa second embodiment of the present invention;

FIG. 15 shows a portion of an example of a processing flow, which iscarried out when remote copying commences on the primary side in a NAScontroller interconnection system related to the second embodiment ofthe present invention;

FIG. 16 shows the remaining portion of an example of a processing flow,which is carried out when remote copying commences on the primary sidein a NAS controller interconnection system related to the secondembodiment of the present invention;

FIG. 17 shows a portion of an example of a processing flow, which iscarried out on the secondary side in a NAS controller interconnectionsystem related to the second embodiment of the present invention;

FIG. 18 shows another portion of an example of a processing flow, whichis carried out on the secondary side in a NAS controller interconnectionsystem related to the second embodiment of the present invention;

FIG. 19 shows yet another portion of an example of a processing flow,which is carried out on the secondary side in a NAS controllerinterconnection system related to the second embodiment of the presentinvention;

FIG. 20A shows an overview of an information processing system relatedto a third embodiment of the present invention;

FIG. 20B is a schematic diagram of an example of processing carried outin a third mode;

FIG. 21A shows an example of a processing flow carried out when a NAScontroller 5 receives a file mount request from a backup server 101;

FIG. 21B shows an example of a processing flow carried out when a NAScontroller 5 receives a file read command from a backup server 101;

FIG. 22 shows an overview of processing carried out by a fourthembodiment of the present invention;

FIG. 23 is an example of a more detailed description of the overview ofthe processing flow shown in FIG. 22; and

FIG. 24 shows an example of a variation of the information processingsystem related to the first embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRRED EMBODIMENT

A number of embodiments of the present invention will be explained belowby referring to the figures.

Embodiment 1

FIGS. 1 and 2 show an information processing system that has a NAScontroller to which a storage control system related to a firstembodiment of the present invention is applied. Connecting FIGS. 1 and 2produces a single information processing system. In the followingexplanation, there will be times when an explanation will use only theparent number when any of the same type of component will do, and timeswhen an explanation will append a branch numeral to a parent number whendistinguishing between the same type of component. Also, in order tomake an explanation easier to understand, there will also be times whenan explanation will not use a branch numeral even when a branch numeralis appended in a figure.

As shown in FIG. 1, a plurality of units (even one unit is fine) ofinformation processing devices 1, and a NAS (Network Attached Storage)controller 5 are connected to a LAN (Local Area Network) 3 (a WAN (WorldArea Network) or other such communications network can also be used).

The respective information processing devices 1, for example, arecomputer devices (for example, personal computers) comprising hardwareresources, such as a CPU, memory and display device. An informationprocessing device 1 can issue a read command for data to be read, or awrite command for data to be written in to a NAS controller 5 (Therewill be times hereinbelow when a read command and write command will bereferred to generically as “access request”). The respective informationprocessing devices 1 can send file level access requests.

A storage device system 2 is connected to the NAS controller 5 so as toenable communications via a prescribed communications interface. The NAScontroller 5, for example, can be constituted from either one or aplurality of circuit boards. The NAS controller 5, for example,comprises a CPU 11, two LAN I/F control portions (for example, LANinterface devices) 13, 13, which are connected to a LAN 3, and two FCI/F control portion (for example, FC interface devices) 15, 15, whichare connected to the storage device system 2 via fibre channels (FC)(There can be either more or less than two LAN I/F control portions 13and FC I/F control portions 15). The NAS controller 5, for example, alsocomprises a data controller 14 for controlling the transfer of databetween the respective LAN I/F control portions 13, CPU 11, memory 7,and respective FC I/F control portions 15, and memory 7 for enablingvarious information to be stored. The CPU 11, for example, can convert afile level access request received from an information processing device1 to a block level access request, and send this block level accessrequest to the storage device system 2. Memory 7, for example, can havea control area for storing control information for controlling theoperation of the NAS controller 5, and a cache area for temporarilystoring data exchanged between an information processing device 1 andlogical volumes 52, 54, which will be explained hereinbelow. The controlarea of memory 7, for example, can store a storage management table 51,reliability comparison table 55 and file comparison table 53. Thesetables will be explained in detail below.

The storage device system 2, for example, comprises a plurality ofchassis connected in series. The plurality of chassis, for example,comprise a base chassis 21, and one or more expansion chassis 23, 23, .. . . The expansion chassis located at the end of the one or moreexpansion chassis 23, 23, . . . connected in series is connecteddirectly to the base chassis 21, and the other expansion chassis areconnected so as to be able to communicate with the base chassis 21 byway of one or more expansion chassis. In order to make the explanationhereinbelow easier to understand, the number of expansion chassis 23will be set at two units (Furthermore, neither the number of basechassis nor the number of expansion chassis is limited to the examplesof FIG. 1 and FIG. 2.)

The base chassis 21, for example, comprises duplexed disk controllers23, 23. Each disk controller 23 can receive a block level access requestfrom the NAS controller 5, and control the input and output of datarelative to logical units 48, 50 explained hereinbelow in accordancewith this access request. For example, a CPU 25, memory 27, datacontroller 29, channel control portion 37, disk control portion 31,cache memory 35 and shared memory 33 are provided in each diskcontroller 23.

Data sent and received between the channel control portion 37 and diskcontrol portion 31 (in other words, data exchanged between aninformation processing device 1 and the logical units 48, 50 describedhereinbelow) is temporarily stored in cache memory 35.

Control information, such as, for example, a table for expressing thecorrespondence of a LUN and an HDD number, is recorded in memory 27.

The channel control portion 37 can send and receive data and controlsignals to and from the NAS controller 5. The disk control portion 31,for example, can send and receive data and control signals for exchangebetween HDD 45, 46 in accordance with a commonly known protocol (e.g.the fibre channel protocol).

The data controller 29 is connected to other data controllers 29 so asto enable communications, thus making possible the exchange of data withother data controllers 29. The data controller 29 can control thetransfer of data between the CPU 25, channel control portion 37, diskcontrol portion 31, cache memory 35, and shared memory 33.

The CPU 25 can execute a variety of information processing. For example,when a block-level read command is received from the NAS controller 5,the CPU 25 can reference control information stored in memory 27,generate a request for reading out the read-targeted data, which iswritten in logical volumes 52, 54 corresponding to a volume ID specifiedin this read command, and send this request by way of the disk controlportion 31. By so doing, the CPU 25 reads out the read-targeted data tocache memory 35, and thereafter, reads this read-targeted data fromcache memory 35 and sends it to the NAS controller 5. Further, forexample, when a block-level write command and write-targeted data arereceived from the NAS controller 5, the CPU 25 temporarily stores thewrite-targeted data in cache memory 35, and can reference controlinformation stored in memory 27, generate, based on this write command,a request for writing the write-targeted data to logical volumes 52, 54corresponding to the volume ID specified in this write command, and sendthis request by way of the disk control portion 31. By so doing, the CPU25 can write the write-targeted data stored in cache memory 35 to thelogical volumes 52, 54 specified by this write command.

As shown in FIG. 2, either the same or different devices can be mountedin the respective expansion chassis 23A, 23B. In this embodiment, theexpansion chassis nearest the base chassis 21 (in this embodiment, 23A)comprises duplexed backend switching devices (hereinafter referred to asbackend SW) 41, 41, and a plurality of physical storage devices 45, 45,. . . connected to both backend SW 41, 41. The expansion chassisfurthest from the base chassis 21 (in this embodiment, 23B) comprisesduplexed backend SW 47, 47, and a plurality of physical storage devices46, 46, . . . connected to both backend SW 47, 47. For example, at leasttwo or more of the plurality of physical storage devices 45, 45, . . . ,or at least two or more of the plurality of physical storage devices 46,46, . . . , can be placed into a single group conforming, for example,to a RAID (Redundant Arrays of Inexpensive Disks) system.

The respective backend SW 41 of expansion chassis 23A are connected tothe respective disk control portions 31 of the respective diskcontrollers 23, and to backend SW 47 of the other expansion chassis 23B.This makes it possible for the disk controller 23 to access the physicalstorage devices 46 inside the expansion chassis 23B, which is locatedfarther away than expansion chassis 23A, by way of the backend SW 41,47.

The respective backend SW 41, 47 comprise I/F-protocol converters 43,49. A block-level access request from a disk controller 23 is convertedto an access request of a format best suited for a physical storagedevice 45, 46 by this I/F-protocol converter 43, 49, making it possibleto write or read data to or from a physical storage device 45, 46.

A physical storage device 45 inside expansion chassis 23A, for example,is used for storing data, which is written and read online. Further, aphysical storage device 46 inside expansion chassis 23B, for example, isused for storing data, which is written and read near-line (for example,batch processing done at night). The physical storage devices 45, 46 inthis embodiment are hard disk drives (hereinafter referred to as HDD),but the present invention is not limited to [HDD], and, for example,other types of drive devices capable of mounting optical disks, magnetictapes or semiconductor memory can also be used. Further, the reliability(or performance) of the physical storage devices 45 provided in theexpansion chassis nearest the base chassis 21 can be made higher thanthe reliability (or performance) of the physical storage devices 46provided in the expansion chassis furthest from the base chassis 21.More specifically, for example, a physical storage device 45 can be anFC interface (hereinafter I/F) HDD (hereinafter FC HDD). Conversely, aphysical storage device 46 can be a SAS (Serial Attached SCSI) I/F HDD(hereinafter SAS HDD). All of a plurality of physical storage devices 46can be SAS HDD, or, instead, can be SATA (Serial ATA) I/F HDD, or can bea combination of SAS HDD and SATA HDD.

A plurality of FC HDD 45, or a plurality of SAS HDD 46, for example, canalso be arranged in an array. Either one or a plurality of logical units(hereinafter, also referred to as LU) can be established in at least oneof the plurality of FC HDD 45. Similarly, either one or a plurality ofLU can be established in at least one of the plurality of SAS HDD 46.(Hereinafter, the reference number of LU on FC HDD 45 will be “48”, andthe reference number of LU on SAS HDD 46 will be “50”.) The logicalstorage areas provided by the respective LU 48, 50 can be furtherpartitioned into a plurality of sub-areas 52, 54. These partitionedsub-areas are called “logical volumes” in this embodiment.

The above is an overview of the information processing system in thisfirst embodiment. Next, the various tables 51, 55 and 53 stored in thememory 7 of the NAS controller 5 will be explained. Furthermore, in thefollowing explanation, deleting both a file and the file-metadatacorresponding thereto will be referred to as “deleting an entire file”,and when a file is deleted, but the file metadata is left, this will bereferred to as “releasing the storage area in which the file resides”.Also, in the following explanation, files in which either all the dataor a part of the data overlap one another will be referred to as“overlap files” (e.g. stated differently “duplicate files”), and datacorresponding to mutually overlapped parts will be referred to as“overlap data”. Therefore, for example, when either all or a part of afirst file and a second file overlap one another, both the first fileand the second file are “overlap files” having “overlap data” (e.g.stated differently “duplicate data”). Hereinbelow, referring to a filesimply as an “overlap file” will denote two files have overlap data, andwhen specifying either one of these files, for example, an expressioncapable of clearly distinguishing the two, such as “one overlap file”and “the other overlap file” will be utilized.

FIG. 3A shows an example configuration of a storage management table 51.

A storage management table 51 is one type of file-metadata group. Astorage management table 51 contains records (file-metadata) comprisingvarious information related to each file stored in either physicalstorage device 45 or 46 of the storage device system 2. As the variousinformation related to a single file (for the sake of convenience, thisis referred to as “file Z” hereinbelow), for example, there are volumeID, path name, filename, data length, attribute information, andinformation of data location for reference(reference locationinformation). Volume ID is the identifier of the logical volume in whichfile Z is stored. Path name is the name denoting the access path to fileZ. Filename is the name of file Z. Data length is the data length offile Z. Attribute information is information denoting attributes relatedto file Z, for example, the timestamp (e.g. date and time) of updating.Reference location information is information indicating the place whereone or more block data corresponding to file Z exist (in other words, aso-called pointer), and, for example, comprises a physical device ID,LUN, TOP LBA, used data length, and link table. A physical device ID isthe identifier of an expansion chassis comprising LU for storing one ormore block data. LUN is the number of the LU for storing one or moreblock data. A top LBA is the logical block address denoting the locationof the beginning data block of one or more data blocks. Used data lengthis the data length resulting from one or more data blocks. The one ormore data blocks corresponding to file Z can be specified using the topLBA and used data length. Furthermore, when file Z is a file thatpartially overlaps another file, the used data length becomes the datalength of this overlapped part. A link table can set an additionaleither one or a plurality of reference location information for file Z.(In the case of a difference file(BNF) or difference file(BOF), whichwill be explained below, file Z can comprise other types of informationto be described hereinbelow.) The total of all used data lengthsincluded in the reference location information of file Z constitutes thefile Z data length.

Every time a new file is stored in a physical storage device 45, 46, theCPU 11 of the NAS controller 5 can add a new record corresponding tothis new file to the storage management table 51. Further, every time afile is deleted from a physical storage device 45, 46, the CPU 11deletes the record corresponding to the deleted file from the storagemanagement table 51, thereby also making it possible to delete theentire file. Further, when a storage area in which either all or a partof one overlap file is released, the CPU 11 can update prescribedinformation inside the record corresponding to this overlap file (thatis, the file-metadata) without deleting this record.

FIG. 3B shows an example configuration of a reliability comparison table55.

Various information related to the respective logical units 48, 50provided in the storage device system 2 are registered in a reliabilitycomparison table 55. As the various information related to one logicalunit (for the sake of convenience, this is referred to a “logical unitZ” hereinbelow), for example, there are a physical device ID, LUN, RAIDlevel, number of HDD units, HDD type, free capacity, device mountdate/time, and reliability ranking. A physical device ID is theidentifier of a physical device having logical unit Z. LUN is thelogical unit Z number. RAID level denotes the RAID level of the RAIDgroup (HDD group) having logical unit Z. The number of HDD units isinformation indicating how many HDD logical unit Z is being provided by.HDD type denotes the classification of the one or more HDD havinglogical unit Z (for example, FC HDD or SAS HDD) (When a plurality oftypes of HDD are intermixed in these one or more HDD, a plurality of HDDtype codes are recorded.) Free capacity denotes the storage capacity ofan area of the storage capacity of logical unit Z in which data is notstored (in other words, a released area). The device mount date/timedenotes the date and time at which the HDD group having logical unit Zwas mounted in an expansion chassis 23 (or, the date and time at whichthis expansion chassis 23 was connected so as to be able to communicatewith the base chassis 21). Reliability ranking denotes the level oflogical unit Z reliability. With regard to the reliability ranking, thehigher the reliability, the lower the number. A different reliabilityranking is set for each logical unit. (The same reliability ranking canalso be set for another logical unit.) For example, when at least one ofthe RAID level and HDD type of a plurality of logical units is the same,either the same reliability ranking or a different reliability rankingcan be set for these respective plurality of logical units. For example,the NAS controller 5 CPU 11 determines the reliability ranking byvaluing the respective components based on at least one of the physicaldevice ID, LUN, RAID level, number of HDD, HDD type, free capacity ordevice mount date/time each time the system administrator changes theconfiguration. (Subsequent to this determination, the reliabilityranking can be set with or without the approval of the administrator.)Here, for example, when reliability valuing is carried out based on RAIDlevel, the reliability ranking can become lower in the order of RAID6+1>RAID 3+1, 4+1 or 5+1>RAID 1>RAID 0+1>RAID 6>RAID 3, 4 or 5>RAID 0.(That is, as one example, RAID 6+1 can be highest, and RAID 0 can be thelowest.) Also, for example, when the valuing is carried out based on HDDtype, the reliability ranking becomes lower in the order of FC>SAS.Further, for example, when the valuing is carried out based on both RAIDlevel and HDD type, as one example, the reliability ranking can bedetermined on the basis of the average value of a reliability rankingdetermined from the standpoint of the RAID level, and a reliabilityranking determined from the standpoint of HDD type (When the averagevalue is the same, the reliability ranking can be determined based onwhichever standpoint takes precedence.).

FIG. 4 shows an example configuration of a file comparison table 53, andan example of one information processing flow that utilizes this table53.

A file comparison table 53 contains records comprising variousinformation related to each file read from either physical storagedevice 45 or 46. As the various information related to a single filethat has been read (for the sake of convenience, this is referred to as“file Y” hereinbelow), for example, there are volume ID, path name,filename, data length, read access timestamp(date/time), and datalocation. Volume ID, path name, filename, and data length are the sameas those registered in storage management table 51. Read accessdate/time denotes the date and time that file Y was read. Data locationis location information denoting where file Y is stored in cache memory35, and/or where records corresponding to file Y are located in thestorage management table 51.

Every time a file is read from a physical storage device 45, 46, the CPU11 of the NAS controller 5 can add a new record corresponding to thisread file at the head of the file comparison table 53, causing thepositions of the already existing records to drop down one,respectively. Thus, file-related records are listed in the filecomparison table 53 in order of read date and time from top to bottombeginning with the most recent date and time. Then, when a predeterminednumber of records has been registered in the file comparison table 53,the CPU 11 can delete the oldest record from the file comparison table53 when the most recent records is newly registered.

The preceding has been an explanation of the file comparison table 53.Furthermore, as mentioned hereinabove, this FIG. 4 also shows an exampleof an information processing flow that uses this table 53, but sincethis explanation will be easier to understand once an overview of theprocessing performed by this embodiment has been explained, this flowwill be explained later by referring to this FIG. 4 once again.

An overview of the processing, which the NAS controller 5 (for example,its CPU 11) carries out in this embodiment, will be explained below.

FIG. 5A is a schematic diagram of processing for copying a file A infolder X to folder Y.

It is supposed that folder X resides in LU0, and that folder Y residesin LU1, which has a lower reliability ranking than LU0. Here, “LU1 has alower reliability ranking than LU0” refers to the fact that the RAIDlevel of LU1 (for example, RAID 5) is lower than the RAID level of LU0(for example, RAID 5+1). Of course, this embodiment is not limited tothis. For example, it could also be a case in which an LU1 HDD (forexample, a SAS HDD) has a lower reliability ranking than an LU0 HDD (forexample, an FC HDD).

The NAS controller 5 can copy file A in folder X to folder Y inaccordance with instructions from an information processing device 1 (orautomatically without receiving these instructions). More specifically,for example, the NAS controller 5 can read file A from folder X byissuing a file read command, and thereafter, can write the read file Ato folder Y by issuing a file write command, thereby copying file A infolder X to folder Y. The NAS controller 5 can add the file-metadatarelated to the read file A at the top of the reliability comparisontable 53, and can add the new file-metadata related to the copy of fileA generated in folder Y (for example, a record comprising the referencelocation information of the data making up this file A) to the storagemanagement table 51.

As explained hereinabove, the NAS controller 5 can store one or aplurality of copies of at least one file in storage resources providedby a plurality of HDD 45, 46 (hereinafter HDD storage resources). Also,for example, subsequent to the generation of a second file, which is acopy of a first file, at least one of the first file and second file isupdated, with the result that the first file and the second file, whichhad been complete overlaps, now become partial overlaps. As this processis repeated, a large amount of overlap data comes to reside in the HDDstorage resources.

In this embodiment, based on the reliability of the LU, it is possibleto leave(or save) at least one or more of a plurality of overlap data,and to free up storage area by releasing storage areas in which otheroverlap data exists. This processing will be explained hereinbelow.Furthermore, in the following explanation, there will be instances when,among the overlap files, a file stored subsequent to this processingwill be called a “update file” (e.g. stated differently “post-updatefile”), and a file stored prior to this processing will be called a “oldfile” (e.g. stated differently “pre-update file”).

FIG. 5B is a conceptual view of an example of releasing an overlap dataarea.

By carrying out the processing shown in FIG. 5A, file A resides in bothLU0 and LU1. That is, the file A, which resides in LU0, and the file A,which resides in LU1, completely overlap one another.

In this case, the CPU 11 of the NAS controller 5 specifies thereliability ranking of LU0 and LU1, respectively, by referencing thereliability comparison table 55. Thus, CPU 11 can specify that a higherreliability ranking has been allocated to LU0 than to LU1.

In this case, CPU 11 releases the storage area in which the file Aoverlap data (in other words, the file A itself here) exists in LU1,which has a low reliability ranking, and leaves the file A in LU0, whichhas a high reliability ranking. Also, in line with releasing the storagearea of the overlap data from LU1, CPU 11 makes the reference locationinformation in the file-metadata corresponding to this LU1 file A (theinformation in the storage management table 51) the same information asthat of the reference location information in the file-metadatacorresponding to the LU0 file A without changing the path name. Thus,CPU 11 can show information processing device 1 that file A exists nomatter which of folder X or folder Y is referenced. However, the datacorresponding to this file A will be read out from LU0 no matter whichof folder X or Y is read.

Further, the CPU 11 records a log relating the fact that a storage areaof overlap data was cleared from LU1 in an overlap file list 403residing in a system volume 402. System volume 402 and overlap file list403 will be explained in detail further below.

FIG. 6A is a conceptual view of another example of releasing an area ofoverlap data. Mainly the points of difference with FIG. 5B will beexplained below, and explanations of the points these two figures havein common will either be omitted or simplified.

By carrying out the processing shown in FIG. 5A, file A resides in bothLU0 and LU1. Then, it is supposed that file A is updated thereafter. Theupdated file A will be called “file A′”. Post-update file A′ resides inLU0, and old file A resides in LU1.

In this case, the CPU 11 of the NAS controller 5 can detect via aprescribed method the fact that the update file A′ residing in LU0 andthe old file A residing in LU1 partially overlap one another. Forexample, this can be detected using an algorithm, which determineseither the LCS (Longest Common Subsequence) or the SED (Shortest EditDistance). Further, CPU 11 can also specify which block data, among aplurality of block data corresponding to update file A′ and two or moreblock data corresponding to old file A, is an overlapped part, and whichblock data is not an overlapped part.

The CPU 11 makes a determination as to whether or not update file A′resides in an LU, which has a higher reliability ranking than old fileA. When a negative determination is achieved as a result of this, theCPU 11 can cause the update file A′ to migrate to an LU, which has ahigher reliability ranking. (At this time, the reference locationinformation of the file metadata of the update file A′ can be updated toinformation denoting the migration-destination location without changingthe path name.) In the example of FIG. 6A, since the update file A′resides in an LU with a higher reliability ranking that the old file A,migration need not be performed.

Further, based on the update file A′ and the old file A, the CPU 11produces a difference file A′-A for restoring the old file A using theupdate file A′. Herein below, a difference file for restoring an oldfile on the basis of an update file means a difference file, which isobtained based on an update file (a new file), and will be called adifference file based on a new file. Conversely, a difference file forrestoring an update file on the basis of an old file means a differencefile, which is obtained based on an old file, and will be called adifference file based on an old file.

The difference file based on a new file (difference file(BNF)) anddifference file based on an old file (difference file(BOF)) will beexplained in detail below. It is supposed that 514-bytes of overlapdata, and 800-bytes of non-overlap data following after the overlap data(hereinafter, old original data) are included in the old file A at thistime. It is also supposed that the same overlap data as above (that is,514-bytes of overlap data), 50-bytes of non-overlap data added in frontof this overlap data (hereinafter, new original data), and 1,000-bytesof new original data following after this overlap data are included inthe update file A′.

In this case, the difference file(BNF) A′-A is a file comprising theinformation required for restoring the old file A from this differencefile(BNF) A′-A and the update file A′. More specifically, for example,the difference file(BNF) A′-A comprises a header, overlap data length,offset information behind of overlap data, and old original datainformation. The header comprises an offset, which denotes how manybytes of new original data there is in front of the first overlap data,in other words, how many bytes need to be skipped from the head of theupdate file A′ to be able to reference overlap data (in this example, 50bytes). The overlap data length is information denoting the data lengthof the first overlap data (in this example, “514 bytes”). Offsetinformation behind of overlap data comprises an offset, which denoteshow many bytes need to be skipped from the end of the first overlap datato be able to reference the next overlap data, and the data length ofthe subsequent overlap data. (Since there is only one overlap data inthis example, the offset is “0” (or null), and the overlap data lengthis “0 bytes”.) Old original data information, for example, comprises theold original data itself. Further, old original data information canalso comprise an offset for showing at what location from the head ofthe old file A this old original data is entered. Old original data andoffset can also be configured as a single set. The number of sets can bethe same as the number of old original data. In this example, there isone set, and this set can comprise 800-bytes of old original data, andthe offset “514 bytes” indicating the location of this old originaldata.

File-metadata of this kind of difference file(BNF) A′-A is also recordedin the storage management table 51. At this time, for example,information related to the header, overlap data length, offsetinformation behind of overlap data, and old original data information ofthe difference file(BNF)A′-A (for example, the locations in thedifference file(BNF) A′-A) can also be defined in the link table insidethis file-metadata.

The CPU 11 of the NAS controller 5 can restore the old file A based onthe above-mentioned difference file (BNF) A′-A and post-update file A′.More specifically, for example, the CPU 11 can specify overlap data fromthe update file A′ by referencing the header, overlap data length, andoffset information behind of overlap data of the difference file(BNF)A′-A. The CPU 11 can also specify old original data in the differencefile(BNF) A′-A by referencing the old original data information of thedifference file(BNF) A′-A. The CPU 11 can restore the old file A bycombining the specified overlap data and old original data on the basisof the old original data information of the difference file(BNF)A′-A.

Next, a difference file based on an old file (difference file(BOF)) willbe explained. A difference file (BOF) A-A′ is a file comprisinginformation required for restoring an update file A′ from thisdifference file (BOF) A-A′ and an old file A. More specifically, forexample, the difference file(BOF) A-A′ comprises a header, overlap datalength, offset information behind of overlap data, and new original datainformation. The header comprises an offset (in this example, “0”),which denotes how many bytes of old original data are in front of thefirst overlap data, in other words, how many bytes need to be skippedfrom the head of the old file A to be able to reference overlap data.The overlap data length is information, which denotes the data length ofthe first overlap data (in this example, “514 bytes”). Offsetinformation behind of overlap data comprises an offset, which denoteshow many bytes need to be skipped from after the first overlap data tobe able to reference the next overlap data, and the data length of thenext overlap data. (In this example, since there is only one overlapdata, the offset is “0” (or null), and the overlap data length is “0bytes”.) New original data information, for example, comprises a set ofnew original data itself, and which location from the head of the updatefile A′ this new original data is entered. The number of these sets canbe the same as the number of new original data. In this example, thereare two sets. The first set comprises 50-bytes of new original data, andoffset “0” denoting the location of this new original data. The secondset comprises 1,000-bytes of new original data, and the offset “564bytes” denoting the location of this new original data.

The CPU 11 of the NAS controller 5 can restore the update file A′ on thebasis of the above-mentioned difference file(BOF)A-A′ and the old fileA. More specifically, for example, the CPU 11 can specify overlap datafrom the old file A by referencing the header, overlap data length, andoffset information behind of overlap data of the difference file(BOF)A-A′. The CPU 11 can also specify new original data in the differencefile(BOF) A-A′ by referencing the new original data information of thedifference file(BOF) A-A′. The CPU 11 can restore the update file A′ bycombining the specified overlap data and new original data on the basisof the new original data information of the difference file(BOF) A-A′.

The explanation will return to FIG. 6A. The CPU 11 writes the differencefile(BNF) A′-A to LU1, and clears the storage area in which the old fileA resides (the storage area in LU1). Pursuant to this processing, theCPU 11 updates the file-metadata related to the old file A in folder Yon LU1. More specifically, for example, the CPU 11 makes the referencelocation information for the overlap data in the old file A the same asthe reference location information for the overlap data in the updatefile A′ (in other words, it sets information denoting the location ofoverlap data in LU0), and makes it the reference location informationdenoting the location in LU1 for the old original data in the old file A(more specifically, the old original data in the difference file(BNF)A′-A) (and adds a link table denoting this information).

Further, the CPU 11 records a log relating the fact that the storagearea in which the old file A resides was cleared from LU1 in an overlapfile list 403 in a system volume 402.

FIG. 6B is a conceptual view of another example of releasing an overlapdata area.

File A resides in LU0. It is supposed that file A is updated afterwards,and that update file A (hereinafter, update file A′) is updated using afilename that differs from file A. This results in both old file A andupdate file A′ residing in LU0 (However, the filenames are different.).

In this case, the CPU 11 of the NAS controller 5 can detect via aprescribed method the fact that the update file A′ and the old file A,which reside in LU0, partially overlap one another.

The CPU 11 produces a difference file(BNF) A′-A on the basis of theupdate file A′ and the old file A. Then, instead of releasing thestorage area in which the old file A resides, the CPU 11 writes thedifference file(BNF) A′-A to a LU, which has a released storage area.Pursuant to this processing, the CPU 11 updates the file-metadatarelated to the old file A (More specifically, for example, updating isthe same as that in the case of FIG. 6A.) Further, the CPU 11 records,in an overlap file list 403 in a system volume 402, a log relating thefact that the storage area in which old file A resided was released fromLU0.

The above is an example of releasing an overlap data area.

This embodiment will be explained in more detail hereinbelow.

Firstly, in order to make the releasing of an overlap data area easierto understand, FIG. 7 and FIG. 8 will be referred to for referencepurposes, and the processing flows for reading a file and writing a filewill be explained in a case in which an overlap data area is notreleased. Thereafter, a file read process and a file write processcarried out in accordance with this embodiment, that is, the flow offile read processing and file write processing when an overlap data areais released, will be explained.

FIG. 7 shows an example of a file read processing flow when an overlapdata area is not released.

When a file read command (a file-level read command) is received, theCPU 11 of the NAS controller 5 checks whether or not the file to beread, which is the target of the read command, resides in a cache areain memory 7 (Step S1).

If the result of S1 is that the read-targeted file is in the cache area(S2: YES), the CPU 11 instructs the data controller 14 to transfer theread-targeted file in the cache area to the information processingdevice 1, which sent the read command (S11). As a result of this, theread-targeted file in the cache area is sent from the data controller 14via a LAN I/F control portion 13 to the information processing device 1where the read command originated (S12).

If the result of S1 is that the read-targeted file is not in the cachearea (S2: NO), the CPU 11 retrieves the file-metadata of theread-targeted file from the storage management table 51 (S3).

If the result of S3 is that the file-metadata of the read-targeted filecannot be found (S4: YES), the CPU 11 reports abnormal end state to theinformation processing device 1 from which the read command originated(S5).

If the file-metadata of the read-targeted file is found as a result ofS3 (S4: NO), the CPU 11 refers to the reference location information inthis file-metadata (In other words, it acquires the storage location ofthe read-targeted file) (S6). Then, the CPU 11 instructs the datacontroller 14 to acquire the data of the read-targeted file (S7). As aresult of this, a read-targeted file data read command is sent from thedata controller 14 to the storage device system 2 via an FC I/F controlportion 15 (S8). Based on this, the data of the read-targeted file isread from either LU48 or LU50, and the read data is transferred to theNAS controller 5 from the storage device system 2 (S9). Then, the datacontroller 14 of the NAS controller 5 stores the data of theread-targeted file in the cache area of memory 7, and the CPU 11 updatesa cache table, which is not shown in the figure (For example, a table,which indicates what location of the cache area the data is stored in)(S10). Thereafter, the above-mentioned S11 and S12 processing arecarried out.

FIG. 8 shows an example of a file write processing flow when an overlapdata area is not released.

When a file-write command (a file-level write command) andwrite-targeted file are received, the CPU 11 of the NAS controller 5retrieves the file-metadata of an old file corresponding to thewrite-targeted file from the storage management table 51 (S21).

If the file-metadata of the old file cannot be found in S21 (S22: YES),then the write-targeted file is a new file, which has not been stored inthe storage device system 2 yet. The CPU 11 instructs the datacontroller 14 to write the write-targeted file into a free area of thelogical volume specified in the write command (S23). Thus, a writecommand for writing the data of the write-targeted file is sent from thedata controller 14 to the storage device system 2 via the FC I/F controlportion 15 (S24). The data of the write-targeted file in either LU 48 or50 is written to the specified logical volume (S25). The CPU 11generates the file-metadata of the written write-targeted file, and addsthis file-metadata to the storage management table 51 (S26).

When the file-metadata of the old file is found in S21 (S22: NO), thewrite-targeted file constitutes an update file of an old file that isalready being stored in the storage device system 2. The CPU 11references the reference location information in the file-metadata ofthe old file (S27). Then, based on this reference location information,the CPU 11 instructs the data controller 14 to update the data of theold file in the update file. (In other words, it overwrites the updatefile with the old file.)(S28) By so doing, an update file write commandis sent from the data controller 14 to the storage device system 2 viathe FC I/F control portion 15 (S29). As a result of this, update filedata is written to either LU 48 or 50 (S30).

When the data size of the update file is smaller than the data size ofthe old file (S31: NO), processing proceeds to S35. When the data sizeof the update file is larger than the data size of the old file (S31:YES), the CPU 11 of the NAS controller 5 instructs the data controller14 to write the surplus data (referred to here as “remaining data”) in afree area of the logical volume to which the update file was written(S32). In accordance with this, a remaining data write command is sentfrom the data controller 14 to the storage device system 2 via the FCI/F control portion 15 (S33). The remaining data is also written intoeither LU 48 or 50 (S34). The CPU 11 of the NAS controller 5 updates thefile-metadata of the written update file (S35). For example, when theupdate file and the old file are exactly alike, the CPU 11 updatesattribute information such as the update date/time. Also, when theabove-mentioned remaining data is stored, for example, the CPU 11 alsoupdates the reference location information in addition to the attributeinformation. (For example, it adds a link table corresponding to theremaining data.)

The NAS controller 5 CPU 11 can send the storage management table 51 tothe storage device system 2, and store it in a storage resource of thestorage device system 2 (for example, either HDD 45 or 46, memory 27,cache memory 35 or shared memory 33).

The above is an explanation of the flows of file read processing andfile write processing when an overlap data area is not released. Next,the flows of file read processing and file write processing in caseswhen an overlap data area is released will be explained.

FIG. 9 shows an example of a file read processing flow when an overlapdata area is released.

S41 through S52 of FIG. 9 are the same as S1 through S12 of FIG. 7.After S52, the NAS controller 5 CPU 11 adds a record comprising aprescribed type of information related to a file, which has been read,to the top of a file comparison table 53 (S53).

FIGS. 10, 11 and 12 show an example of a file write flow when an overlapdata area is released. For the sake of convenience, the write processwill be explained hereinbelow by referring to FIG. 4 in addition tothese figures. Furthermore, the processing flow shown by FIG. 10, FIG.11 and FIG. 12 is the flow for writing a so-called new file when thefile-metadata of an old file, which is the write-targeted file, does notexist in the storage management table 51. However, this process is notonly for when a write-targeted file is a new file, but can also beapplied in the case of a update file.

When a determination has been made that a write-targeted file is a newfile, as shown in FIG. 10, the same processing as in S23 through S26 ofFIG. 8 is carried out (S61 through S64). Hereinbelow, the data of thenew file will be called “first data”. Furthermore, in the case of remotecopying, which will be explained hereinbelow, the CPU 11 can save firstdata to either the cache area of the NAS controller 5 or the cachememory 35 of the storage device system 2, and then transfer this firstdata from either the cache area or cache memory 35 to the copydestination.

The NAS controller 5 CPU 11 references the record at the head of thefile comparison table 53 (S65), and acquires the reference locationinformation of files that have been marked in this file comparison table53 from the storage management table 51 (S66). Here a “marked file” is afile corresponding to a record, which exists in the file comparisontable 53. As shown in FIG. 4, the CPU 11 compares the data of the markedfile, which resides in the location denoted by the reference locationinformation acquired in S66 (hereinafter referred to as “second data”),against the first data (S67).

When the result of S67 is that there is no partial matching area (inother words, overlap data) of one block (for example, 512 bytes) ormore, if the record referenced in S65 was not the last record in thefile comparison table 53 (S74: NO), processing returns once again toS65. When the record referenced in S65 was the last record in the filecomparison table 53 (S74: YES), the CPU 11 retrieves the file metadataof a file with a filename and/or a data length that is the same as thefirst data (hereinafter, the data of this file will be called the “thirddata”) from the storage management table 51 (S75). When thefile-metadata of the third data is not found, processing can beterminated. When the file-metadata of the third data is found, the CPU11 compares the first data against the third data residing in a locationdenoted by the reference location information in this file-metadata(S76).

When S76 results in a partial matching area of one block or longer (S77:NO), and all the data matches (S69: YES), S70 processing, which will beexplained hereinbelow, is carried out, and when there is partialmatching (S69: NO), S81 processing of FIG. 12 is carried out. When S76does not result in a partial matching area of one block or longer (S77:YES), S75 processing is performed once again, provided the file-metadatafound via the S75 retrieval is not file-metadata residing in the finallocation of the storage management table 51 (S78: NO).

Now then, when either S67 or S76 results in a partial matching area ofone block or longer (Either S68 or S77 of FIG. 11: NO), and all the datamatches (S69: YES), S70 processing, which will be explained below, iscarried out. That is, as shown in FIG. 4 as well, the CPU 11 referencesthe reliability comparison table 55, and compares the reliabilityranking of the LU of the second data (or the third data) against thereliability ranking of the LU of the first data (S70). The CPU 11updates the reference location information of the data with a lowreliability ranking with the reference location information of the datawith a high reliability ranking (S71). The CPU 11 releases the storagearea of the data with a low reliability ranking (S72). The CPU 11registers information related to the first data and the second data (orthe third data), which are complete overlaps (for example, all or partof the respective file-metadata), and the fact that the area in whicheither one of these first data and second data (or third data) residedhas been released in the overlap file list 403 in the system volume 402(S73).

When either S67 or S76 results in a partial matching area of one blockor longer (Either S68 or S77 of FIG. 11: NO), but not all the datamatches (S69: NO), S81 processing of FIG. 12 is carried out. That is,the CPU 11 produces a difference file(BNF) based on the first data(update file) and either the second data or the third data (old file)(S81). The CPU 11 references the reliability comparison table 55, andcompares the reliability ranking of the LU of the first data(hereinafter, the first LU) and the reliability ranking of the LU of thesecond data (or the third data) (hereinafter, the second LU) (S82).

When the reliability ranking of the first LU is higher than that of thesecond LU in S82 (S83: NO), processing S87 which will be explainedhereinbelow is carried out.

On the other hand, when the reliability ranking of the first LU is lowerthan that of the second LU in S82 (S83: YES), the CPU 11 issuesinstructions to the data controller 14 to write the first data to thesecond LU (S84). Thus, the first data is written to the second LU, whichhas a higher reliability ranking (S85). The CPU 11 updates the referencelocation information of the first data with information denoting thelocation of the write destination in the second LU (S86).

The CPU 11 issues instructions to the data controller 14 to write thedifference file(BNF) to an LU with a low reliability ranking (S87).Accordingly, the difference file(BNF) is written from the datacontroller 14 via the FC I/F control portion 15 to an LU with a lowreliability ranking (S88). The CPU 11 clears the area in which at leasteither the second data or the third data (in addition, for example, thefirst data residing in an LU with a low reliability ranking) resides(S89).

The CPU 11 updates the second storage management table 51 (S90). Morespecifically, for overlap data of the first data and second data (orthird data), the CPU 11 updates reference location informationindicating the area in which this overlap data resides in an LU with ahigh reliability ranking, and for the old original data in thedifference file(BNF), it updates reference location informationindicating the area in which this old original data resides in an LUwith a low reliability ranking (or an LU with the same reliabilityranking).

The CPU 11 updates the overlap file list 403 of the system volume 402(S91). More specifically, the CPU 11 records in the overlap file list403 that fact that the first data and the second data (or the thirddata) overlap one another (It can also record the fact that the seconddata area has been cleared, and the difference file(BNF) written to anLU with a low reliability ranking.) The above is an example of a writeprocessing flow.

The yet to be explained system volume 402 and overlap file list 403 willbe explained hereinbelow.

The system volume 402, for example, is a logical volume, which cannot beaccessed from the information processing device 1 (a logical volume towhich at least a write operation from the information processing device1 is prohibited). System information related to the control of thestorage device system 2 is stored in the system volume 402, and the CPU25 of the storage device system 2 can read in this system informationfrom the system volume 402, and carry out operations based on thissystem information. The overlap file list 403 is what is called a logfile. Files that completely or partially overlap other files, and whichfiles overlap which other files, is recorded in the overlap file list403 (The entire or partial areas of the data of those overlap files thathave been released can also be recorded.) More specifically, forexample, information such as

(1) [Source] Path¥Filename (File Handle; Metadata Location, etc.)

(2) [Copy] Path¥Filename (File Handle) Copy Date/Time

(Complete Overlap or Partial Overlap)

can also be recorded in the overlap file list 403. Here, the [Source] of(1) can be thought of as the overlap data, which has been left, ratherthan the overlap data storage area, which has been released, regardlessof whether it is an old file or an update file. In relation to this, the[Copy} of (2), by contrast, can be thought of as the released area amongthose mutually duplicating files for which an overlap data storage areahas been released, and not the overlap data that has been left.

As shown in FIG. 13A, the NAS controller 5 CPU 11, for example, can,based on this overlap file list 403, display those files that overlapone another on a specified device (For example, either the informationprocessing device 1 or a not-shown terminal utilized by a systemsadministrator (hereinafter, administrator's terminal)). Also, forexample, when instructions to delete a certain overlap file are receivedfrom the above-mentioned specified device (hereinafter, “specifieddevice”), the CPU 11 can delete this overlap file by deleting thisoverlap file and its file-metadata. More specifically, for example, whenthe overlap file for which delete instructions were issued is an oldfile, the CPU 11 can delete this old file by deleting the leftdifference file(BNF) and the file-metadata of the old file. Also, forexample, when the overlap file for which delete instructions were issuedis an update file, the CPU 11, as shown in FIG. 13B, can delete thisupdate file A′ by reconstructing old file A using the left differencefile(BNF) A′-A and update file A′, and deleting update file A′ and itsfile-metadata. Further, once an overlap file has been deleted, the CPU11 can also delete information related to this overlap file from theoverlap file list 403. For example, using the example of FIG. 13B, whenupdate file A′ is deleted, the CPUI 11 can delete information related tothe pair of files constituted by this update file A′ and the old file A.

Further, the NAS controller 5 CPU 11, for example, can specify justwhich files overlap which other files by referencing the overlap filelist 403 as shown in FIG. 13C. The CPU 11 can execute specificationprocessing based on the results of specification. For example, when theCPU 11 specifies two or more files, which either completely or partiallyoverlap a certain file, in other words, when it specifies three or morefiles that overlap one another, it can delete files with the exceptionof at least two files. Further, the CPU 11 can leave a file that residesin an LU with a high reliability ranking at this time, and it canmigrate the left file to an LU with a higher (or the highest)reliability ranking.

Also, the NAS controller 5 CPU 11 can also specify which, of a pluralityof files residing in storage device system 2, do not overlap other filesby also referencing, for example, the storage management table 51 inaddition to the overlap file list 403. In this case, as shown in FIG.13C, for example, the CPU 11 can migrate a file that is not overlappedfrom the first LU, where this file is currently residing, to the secondLU, which has a low reliability ranking, and release the area of thenon-overlap file from the first LU, thereby increasing the free storagecapacity of the first LU.

According to this first embodiment described hereinabove, of two filesthat overlap one another, the file that is in a location with a highreliability ranking will be left, and the area of the file that is in alocation with a low reliability ranking will be released. When an oldfile and a post-update file partially overlap one another, and thepost-update file is in a location with a low reliability ranking, theold file is released after being migrated to a location with a highreliability ranking. Such processing makes it possible to reduce thestorage capacity being used, while lowering the risk that a file will belost.

Also, according to this first embodiment, the scope of overlap fileretrieval carried out at file write is not all files residing in thestorage device system 2, but rather, is narrowed to one or more filesread out near the point in time of this write (For example, eitherfiles, which were read within a prescribed time period from the time ofthe write, or a prescribed number of files, which were read near thetime of the write). This is efficient from the following standpoint.That is, for example, when a file is to be copied from one folder toanother folder in accordance with a command from an informationprocessing device 1, an old file is read from the one folder and writtento either the same or a different folder as an update file. At thistime, the write processing of either a certain file or an update filerelative thereto is carried out in a relatively short period of time(for example, within 24 hours) following the read processing for thecertain file. Therefore, as explained hereinabove, setting the scope ofoverlap file retrieval to one or more files read near the point in timeof the file write is considered efficient from the standpoint ofdetecting overlap files. At least it is possible to find overlap filesin a shorter period of time than it takes to retrieve overlap filesusing the brute force method.

Also, in accordance with this first embodiment, the difference filegenerated when an old file and an update file partially overlap oneanother is not a difference file(BOF), but rather a differencefile(BNF). This is considered more efficient than generating and savinga difference file(BOF) rather than a difference file(BNF). This isbecause, when it comes to which of the old file and update file will bedeleted, it is felt there is a greater likelihood of the old file beingdeleted than the update file. More specifically, for example, this isbecause, when an old file is deleted, if there is a system for saving adifference file(BNF), deletion can be carried out by simply deleting thefile-metadata corresponding to the old file and the differencefile(BNF), but if the system leaves a difference file(BOF), then it isnecessary to reconstruct an update file using the difference file(BOF)and the to-be-deleted old file.

Further, in accordance with this first embodiment, when an overlap fileis detected, information related to the files, which overlap oneanother, is recorded in an overlap file list 403. If a systemadministrator or user should request to be informed of the overlap filesresiding in the storage device system 2, since the presentation of thisinformation can be carried out based on the overlap file list 403, therequested information can be presented in a shorter period of time thanit would take to carry out retrieval once again.

In this first embodiment, when an overlap file is detected, informationrelated to the detected overlap file is recorded in the overlap filelist 403 at a prescribed timing (for example, when the storage area ofat least one of the overlap data is released). By so doing, thereafterit is possible to specify the overlap file from the information recordedin the overlap file list 403. More specifically, for example, the CPU 11can provide the information recorded in this overlap file list 403 tothe above-mentioned specification device (for example, either theinformation processing device 1 or the administrator's terminal), and ifthis information is displayed, the operator of the specification device(for example, a user or administrator) can easily specify the overlapfile. Or, for example, the CPU 11 can rapidly specify which files areoverlap files by referencing the overlap file list 403.

In other words, in this first embodiment, after an overlap file has beendetected, information as to which files are overlaps is not recorded inthe storage management table 51, but rather is recorded in an overlapfile list 403 prepared separately from the storage management table 51.

For example, when three or four copies of a file have been prepared, itis possible that one copy is a copy of another copy. Creating an area inthe storage management table 51 for accurately detecting just whichcopies are copies of other copies is not viewed as efficient. Further,in addition to the retrieval operation carried out when one file iscopied, it is also necessary to retrieve the overlap of the file of thiscopied file. In this case, if the overlap file list 403 listed up allthe overlap files in the storage device system 2, it would be possibleto specify an overlap file by retrieving the contents of the list 403,thereby enabling a smaller scope of retrieval than a method thatutilizes the storage management table 51. As a concrete example of this,after creating file B, which is the update file of file A, file C, whichis the update file of file B, is created, and when update file C ismigrated to the LU where file B resides, referencing the overlap filelist 403 makes it possible to rapidly specify file A as the file thatoverlaps file B, as well as the location of the file-metadata of file A.

Furthermore, in this first embodiment, with regard to the informationrelated to overlap files recorded in the overlap file list 403, forexample, even if one file has multiple overlap files, recording theinformation related to the overlap files on a one-to-one basis isconsidered preferable to recording it on a one-to-N basis. Morespecifically, for example, when one file A has two overlap files B, C,it is considered preferable to record them separately as file A and fileB, and file A and file C. By so doing, for example, when file A of fileA and file B is deleted, the file-metadata related to file B is updated,doing away with the need to update metadata related to file C.

Embodiment 2

A second embodiment of the present invention will be explainedhereinbelow. Furthermore, mainly the points of difference with the firstembodiment explained above will be explained below, and explanations ofpoints shared in common with the first embodiment will either be omittedor simplified (The same will also hold true for the other embodimentsexplained hereinbelow.)

FIG. 14 shows an overview of an information processing system related toa second embodiment of the present invention.

This information processing system is a system for enabling what iscalled remote copying. For example, there are a primary NAS controller5A and a secondary NAS controller 5B. A primary storage device system 2Ais connected to the primary NAS controller 5A, and a secondary storagedevice system 2B is connected to the secondary NAS controller 5B. Thesecondary storage device system 2B (for example, its base chassis) isconnected via a leased line or communications network to the primarystorage device system 2A (for example, its base chassis) to enablecommunications (solid lines in the figure).

An example of an overview of the processing carried out by thisinformation processing system is as follows.

For example, first, all the data residing in a user data area (forexample, an area on an HDD storage resource other than a system volume)501A in the primary storage device system 2A is copied to an HDD storageresource on the secondary storage device system 2B, thereby providingthe same area 501B as the user data area 501A of the primary storagedevice system 2A in the secondary storage device system 2B.

Further, the above-mentioned various tables 51, 53, and 55 are recordedin a prescribed metadata area (for example, shared memory 33) 502A inthe primary storage device system 2A. These tables 51, 53 and 55 arealso transferred to the secondary storage device system 2B, therebyproviding the same area 502B as the metadata area 502A of the primarystorage device system 2A in the secondary storage device system 2B.

Next, for example, when a file, which is a complete overlap of a certainfile residing in the user data area 501A, is stored in this area 501A,either the NAS controller 5 or the disk controller 23 (for example,either CPU 11 or 25) records the file-metadata of the newly storedoverlap file in the storage management table 51. In this case, theprimary storage device system 2A (for example, the disk controller 23)transfers the new overlap file-metadata to the secondary storage devicesystem 2B. The transferred file-metadata is added to the storagemanagement table in the secondary storage device system 2B. Thus, thedata of the new overlap file itself is not actually stored in thesecondary storage device system 2B, but it makes it possible for theinformation processing device 1 to recognize the new overlap file asresiding in the secondary storage device system 2. More specifically,for example, the secondary NAS controller 5B can make the informationprocessing device 1 recognize the new overlap file based on thefile-metadata newly recorded in the storage management table in thesecondary storage device system 2B.

Thus, when a second file, which completely overlaps a first file, whichis already stored in the user data area 501A, is written to the samearea 501A, if the storage area of the second file has been released, thedata transferred for remote copying can be limited to the file-metadataof the second file. That is, since there is no need to transfer thewritten file itself, it is possible to reduce the amount of data to betransferred.

However, it is not considered desirable to simply convert this remotecopying system to the remote copying carried out when a partiallyoverlapped update file is written to the user data area 501A under ananother filename. This is because, when a simple conversion is carriedout, the file-metadata of the update file, the difference file(BNF) andits file-metadata must also be transferred in addition to the updatefile itself, thereby increasing the amount of data to be transferred.

Accordingly, in order to avoid this problem, as shown in FIG. 14, eitherinstead of or in addition to the storage device systems 2A, 2B beinginterconnected to enable communications, it is possible to adopt asystem in which the NAS controllers 5A, 5B are interconnected to enablecommunications (hereinafter, the NAS controller interconnection system)(the dotted line in the figure). An example of the flow of processingcarried out by the primary and secondary sides in this NAS controllerinterconnection system will be explained hereinbelow.

FIG. 15 and FIG. 16 show an example of the processing flow carried outwhen remote copying is commenced on the primary side in a NAS controllerinterconnection system.

The NAS controller 5A retrieves an update carried out subsequent to thelast remote copy (S101). Thus, for example, the NAS controller 5A canstore the date and time of a remote copy processing termination inmemory, and can retrieve an update carried out subsequent to the lastremote copy by comparing this date and time against the update date andtime in the file-metadata of the storage management table 51.

The NAS controller 5A acquires reference location information denotingthe location of an update carried out subsequent to the last remotecopy, from the storage management table 51 (S102).

When the result of S102 is that the data residing in the acquiredreference location information-denoted location is data of a completelyoverlapped file (S103: YES), the NAS controller 5A sets the flag insidethe metadata header information to “Overlap Data”, and sets the headeroption to “No” (S104). Here, metadata header information is theinformation set in the header of the information comprising thefile-metadata sent from the NAS controller 5A. The NAS controller 5Atransfers the file-metadata of an overlap file written afterwards andthe information comprising the above-mentioned metadata headerinformation to the NAS controller 5B (S105). Thereafter, S118 of FIG.16, which will be explained below, is carried out.

When the result of S102 is that the data residing in the acquiredreference location information-denoted location is a new file (S103: NO,S106: NO), the NAS controller 5A acquires this new file by sending aread command for this new file to the storage device system 2A (S107),and storing it in a cache area (S108). Further, the NAS controller 5Asets the flag in the metadata header information to “New Data”, and setsthe header option to “No” (S109). The NAS controller 5A sends the newfile stored in the cache area, the file-metadata of this new file, andthe information comprising the metadata header information in S109 tothe NAS controller 5B (S110). Furthermore, when either all or a part ofa file, which was received for a write operation subsequent to the lastremote copy, was saved in the cache area, and the new file is stillsaved in the cache area, the NAS controller 5A can send the new file tothe NAS controller 5B without carrying out the processing of S107 andS108.

When the result of S102 is that the data residing in the acquiredreference location information-denoted location is a partiallyoverlapped update file (S103: NO, S106: YES), the NAS controller 5Aacquires this update file by sending a read command for this update fileto the storage device system 2A (S111), and storing it in the cache area(S112).

The NAS controller 5A also specifies a difference file(BNF)corresponding to the acquired update file by referencing the storagemanagement table 51, acquires the specified difference file(BNF) fromthe storage device system 2A, and stores the acquired differencefile(BNF) in the cache area (S113). Further, the NAS controller 5Areconstructs an old file from the update file and difference file(BNF)in the cache area, generates a difference file(BOF) based on the oldfile and update file, and stores the generated difference file(BOF) inthe cache area (S114). The NAS controller 5A sets the flag inside themetadata header information to “Updated Data”, and sets the headeroption to “Yes” (S115).

The NAS controller 5A also adds to the header option the informationrequired for the NAS controller 5B to retrieve the same old file as thereconstructed old file from the storage device system 2B (S116). Thereference location information of the old file on the secondary side,for example, can be used as the “Required Information”. For example, theNAS controller 5A can specify this reference location information byassociating the reference location information of this old file toeither the file-metadata of the update file or the file-metadata of thedifference file(BNF) when the old file area is released from the storagedevice system 2A. The NAS controller 5A sends information comprising thedifference file(BOF) generated in S114 and the metadata headerinformation from S115 and S116 to the NAS controller 5B.

Furthermore, the above-mentioned header option is information thatordinarily does not have to be in the header, and when it does exist inthe header, is there for executing a specification function. Forexample, when retrieval path/filename/area information and the like isincluded in a header and transferred as the header option, the sidereceiving the information comprising this header option can retrieve afile based on this header option.

When the above processing has been carried out for all files updatedafter the last remote copy was performed (S118: YES), processing isterminated, and when it has not (S118: NO), the determination of S103 ofFIG. 15 is made for the next unprocessed file.

FIGS. 17, 18 and 19 show an example of the processing flow carried outon the secondary side in a NAS controller interconnection system.

When the NAS controller 5B receives information comprising metadataheader information from the NAS controller 5A, it checks the flag inthis metadata header information (S121).

If the result of S121 is a flag for new data (S122: YES), the NAScontroller 5B writes the new file included in the received informationto the location denoted by the reference location information of thefile-metadata of this new file (S123). Further, the NAS controller 5Badds the file-metadata of this new file to the storage management table51 (S124). Thereafter, the processing of S135 of FIG. 18 is carried out.

If the result of S121 is a flag for overlap data (S122: NO, S125: YES),the NAS controller 5B specifies the file-metadata corresponding to thefile-metadata of the old file (one of the overlap files) included in thereceived information from the storage management table 51, and acquiresthe reference location information in this specified file-metadata(S126). The NAS controller 5B uses the reliability comparison table 55to compare the reliability ranking of the LU, in which the overlap filein the acquired reference location information-denoted location isstored, against the reliability ranking of the LU having astorage-scheduled area (the LU denoted by the file-metadata of theupdate file (the other overlap file)) (S127).

When the result of S127 is that the reliability ranking of thestorage-scheduled area LU is low (S128 of FIG. 18: NO), the processingof S133 is carried out. When the result of S127 is that the reliabilityranking of the storage-scheduled area LU is high (S128 of FIG. 18: YES),the NAS controller 5B reads the old file (the one overlap file) from theLU with the low reliability ranking (S129, S130), and writes the readold file to the storage-scheduled area (S131). Then, the NAS controller5B releases the area in which the read overlap file resides from the LUwith the low reliability ranking (S132). The NAS controller 5B adds thefile-metadata related to the write file (that is, the file-metadata ofthe update file received from NAS controller 5A) to the storagemanagement table 51, and updates the file-metadata of the file whosearea was released (S133).

The NAS controller 5B updates the overlap file list inside the systemvolume in the storage device system 2B (S134). For example, when the NAScontroller 5B updates the overlap file list by carrying out theprocessing of S126 through S133, it adds information related to files,which completely overlap one another, to the overlap file list.

Further, the NAS controller 5B sends the file-metadata added to andupdated in the storage management table 51 to the storage device system2B (S135). Thus, the storage management table in the storage devicesystem 2B is updated, with the result that this storage management tableconstitutes the same contents of the update storage management table 51in the NAS controller 5B. Furthermore, the NAS controller 5B need notcarry out the processing of this S135 each time S134 is carried out, butrather, for example, when the updated file-metadata reaches apredetermined number, can carry out S135 for the file-metadata of thispredetermined number of updates.

If the result of S121 is a flag for updated data (FIG. 17 S122: NO,S125: NO), the NAS controller 5B specifies the file-metadatacorresponding to the file-metadata of the old file included in thereceived information from the storage management table 51 (S136 of FIG.19). The NAS controller 5B reads the old file from the referencelocation information in this specified file-metadata (S137, S138). TheNAS controller 5B creates an update file based on the read old file anda difference file(BOF) in the received information, and creates adifference file(BNF) on the basis of this update file and old file(S139). The NAS controller 5B uses the reliability comparison table 55to compare the reliability ranking of the LU of the read old fileagainst the reliability ranking of the LU of the storage-scheduled areaof the created update file (the LU denoted by the file-metadata of theupdate file in the received information) (S140). When the LU of thestorage-scheduled area of the update file has a high reliabilityranking, the NAS controller 5B writes the created post-update file tothis storage-scheduled area LU (S141). Further, the NAS controller 5B adifference file(BNF) based on the created update file and the read oldfile to an LU with a low reliability ranking (or an LU with the samereliability ranking) (S142). Further, the NAS controller 5B releases thearea in which the read old file resides (S143). The NAS controller 5Bupdated the storage management table 51 in accordance with the updatefile write, the difference file(BNF) write, and the releasing of the oldfile area. Thereafter, the processing of the above-mentioned S134 andS135 of FIG. 18 is carried out.

Thus, since the secondary-side NAS controller 5B can eliminate the needto transfer the update file and difference file(BNF) by creating theupdate file and difference file(BNF), it is able to reduce the amount oftransferred data.

Furthermore, instead of sending a difference file(BOF) and generating anupdate file and difference file(BNF) from this difference file(BOF) onthe secondary side, the constitution can also be such that the need togenerate an update file is eliminated by transferring an update file.Furthermore, the selection as to which system to employ can be suitablymade based on instructions from either a user or system administrator,or can be made automatically by either the NAS controller 5 or the diskcontroller 23 based on a prescribed condition. As the prescribedcondition, for example, when the data size of the update file is lessthan a prescribed size, and as such will not have a significant impacton data transfer, the system whereby the update file itself istransferred can be selected, and when this is not the case, the systemwhereby a difference file(BOF) is created and transferred can beselected.

Embodiment 3

A third embodiment of the present invention will be explainedhereinbelow.

FIG. 20A shows an overview of an information processing system relatedto a third embodiment of the present invention.

A backup server 101 is connected to a LAN 3. A tape library 103 isconnected to the backup server 101. A tape system 105 utilizing a tapeas a storage is connected to the tape library 103 as a storage device.The tape library 103 is directly connected to the backup server 101 inthis example, but it can also be connected to the backup server 101 viaa LAN 3 or other communications network. The tape library 103 can readand write data to a built-in tape system 105. The tape system 105ordinarily has a plurality of tape decks for high-speed processing, butthese tape decks are not shown in the figure here. Further, to keep themodel simple, the figure shows one LU stored on one stowable tape of thetape library 103. More specifically, for example, as shown in thefigure, LU0 data is stored on a tape 1, and LU1 data is stored on a tape2.

A backup server registration table 102, for example, is stored in memory7 in the NAS controller 5. Specified backup server-related information(for example, an identifier) is registered in advance in the backupserver registration table 102 by a specified person (for example, thesystems administrator).

The same file A resides in LU0 and LU1 of the storage device system 2(hereinafter, primary LU0, LU1). Both file A are made recognizable tothe information processing device 1 by the NAS controller 5, and thefile A residing in primary LU0 is made recognizable to the backup server101 registered in the table 102, but the file A residing in primary LU1is hidden. Thus, hiding at least one overlap file from the registeredbackup server 101, for example, prevents a file of the same content frombeing backed up multiple times, thereby making it possible to reduce theamount of data to be backed up. As a result of this, it is also possibleto shorten the time required for backup.

A file (hereinafter, metadata aggregate file) X, in which is recordedthe file-metadata of various overlap files residing in the storagedevice system 2, is also recorded in primary LU1. Further, the NAScontroller 5 makes the metadata aggregate file X in the storage devicesystem 2 recognizable to the backup server 101 so that even theabove-mentioned hidden file can be completely restored to its originalstate at data restoration. In FIG. 20A, the backup server 101 recognizesthe metadata aggregate file X as being in LU1, which is a storage areawith lower reliability. As a result of this, for example, the metadataaggregate file X is read out of the primary LU1 by the backup server101, and stored in the secondary LU1 (LU1 in tape 2).

In this third embodiment, at least one of three modes, a first, secondand third mode, is used.

(A) First Mode

In the case of a NAS, which carries out backup using a file image,backup is achieved by sequentially executing read processing from theinformation processing device 1. For this reason, unless some sort ofmechanism is put in place, there is no hope of reducing the amount ofdata because two files that overlap one another are read, and both readfiles are transferred to the backup server 101.

Accordingly, in this first mode, when the NAS controller 5 determines anaccess from the registered backup server 101, it only hides the overlapfile i-node of the file i-node tree from the backup server 101, makingthe file invisible. This makes it possible to reduce the amount of datatargeted for backup. (In other words, it becomes possible to shorten thetime required for backup.) More specifically, for example, all the datain the primary LU0 is recognized by the backup server 101, and as aresult, all the data from the primary LU0 can be read, and backed up onthe LU0 of tape 1 (hereinafter, secondary LU0).

In this first mode, the restoration of all files other than overlapfiles can be carried out on the tape system 105. With regard tounrestored overlap files, for example, restoration can be carried outbased on the old file (the file which constitutes the original) in thesecondary LU0, and the metadata aggregate file X, which was copied tothe secondary LU1 (tape 2 LU1) from the primary LU1. Further, once thisrestoration is complete, the metadata aggregate file X can be deletedfrom the tape system 105.

Furthermore, when an access is received from a backup server that hasnot been registered in advance in the NAS controller 5, the NAScontroller 5 can show this unregistered backup server all the filesincluding the overlap files. In this case, all the files can be read tothis previously unregistered backup server.

Furthermore, the NAS controller 5 can read in an update file anddifference file(BNF) from the storage device system 2, restore an oldfile on the cache area based on the read-in update file and differencefile(BNF), and transfer the restored old file to the backup server 101.

Also, as explained hereinabove, the NAS controller 5 can collecttogether the file-metadata of the files in an invisible state in LU1 andwrite it to a certain LU (for example, LU1 shown in the figure) as asingle metadata aggregate file X so as to enable these invisible filesto be restored to their previous states at restoration time. In thiscase, restoration is made possible while striving to reduce the amountof data by virtue of the backup server 101 reading out the hidden filebased on the information written to this metadata aggregate file X, andwriting it to an LU in the tape system 105 via the tape library 103.

Also, for example, file attributes that make it possible to distinguishbetween other ordinary files can also be set in the metadata aggregatefile X, or, steps can be taken so as to enable files to be identifiedusing paths (folders)/filenames managed by either the NAS controller 5or disk controller 23. In this case, the NAS controller 5 canreconstruct the storage management table (For example, processing forupdating reference location information in file-metadata usinginformation denoting the location where real file data actually exists.)using real files, which reside in an LU with a higher reliabilityranking than the LU in which files specified from the pertinent metadataaggregate file X are stored (That is, files that actually exist as datarather than files that exist virtually as a result of clearing a storagearea.).

(B) Second Mode

The second mode backs up the difference file(BOF) or differencefile(BNF) itself. In this case, it is possible to hold down the storagecapacity required by a tape of the tape system 105. That is, in thefirst mode, an old file is restored on the basis of an update file and adifference file(BNF), and this restored old file is provided to thebackup server 101, but in the second mode, the difference file(BNF) isprovided as-is to the backup server 101. Thus, it is possible to reducethe amount of data being backed up more than in the first mode. However,in this second mode, since it can be necessary for the backup server 101to create an old file based on a difference file(BNF), this functionmust be provided to a backup server that does not have such a function.

(C) Third Mode

A physical address image of the storage device system 2 (for example, avolume image or a LU image) is treated as a file, and this file istransferred to the backup server 101. More specifically, for example, asshown in the example in FIG. 20B, the NAS controller 5 makes a file ofphysical address images in 1 GB continuous block units from the head ofthe LBA, and transfers this file (hereinafter, the physical addressimage file) to the backup server 101. The backup server 101 writes thisphysical address image file to a tape of the tape system 105 by way ofthe tape library 103.

According to this third mode, restoration, which completely matches thecontents of the storage device system 2, can be carried out on the tapesystem 105. In other words, the third mode is effective in cases whereinthere is a large amount of data used in a certain storage area (forexample, either a LU or a logical volume) of the storage device system2, and can hold down on the storage capacity required on a tape byreducing the filename and path name information stored on the tape.Here, “the amount of data used” is the amount of data (files) occupyinga certain storage area.

Further, reducing the number of times that commands and states arecommunicated each time a file is read not only enhances data transferefficiency, but also makes it easy for the storage device system 2 toprefetch subsequent data, enabling the reduction of hard disk seek timeand other such waiting time.

For the systems administrator, the fact that data size does not changeregardless of the number of files makes it easy to calculate theallocation of storage capacity (for example, tapes) at full backup time.

Furthermore, for example, if the NAS controller 5 stores the length oftransfer time that is predicted for full backup (hereinafter, predictedtransfer time length) and the length of the previous access time of aregistered backup server 101 (data transfer time length) in memory 7, itwill also be possible to transfer at the subsequent access time adifference image from the previous time based on the difference betweenthe predicted transfer time length and the previous access time length(the data length of the respective region image files will becomesmaller).

Now then, for example, selecting which of the above-mentioned first modethrough third made is to be used can be made either manually orautomatically. More specifically, for example, the NAS controller 5accepts which mode of the first mode through the third mode will be usedby the either information processing device 1 or the not-shownadministrator's terminal, and when it receives a mode selection, cancarry out backup in accordance with this selected mode.

An example of the flow of processing carried out by this thirdembodiment will be explained hereinbelow.

FIG. 21A shows an example of the flow of processing carried out when theNAS controller 5 receives a file-mount request from the backup server101.

The NAS controller 5 makes a determination as to whether or not theidentifier of the backup server 101, which is the transmission source ofan access command (for example, a read command), has been registered inadvance in the backup server registration table 102 (S151).

When the results of S151 are that the transmission-source backup server101 is not registered (S151: NO), and does not have access rights (S152:NO), the NAS controller 5 returns a reply signifying that access isdenied (S153).

When the results of S151 are that the transmission-source backup server101 is not registered (S151: YES), but does have access rights (S152:YES), the NAS controller 5 returns a reply signifying that access isapproved (S157).

When the result of S151 is that the transmission-source backup server101 is registered (S151: YES), the NAS controller 5 determines which ofthe first through the third mode has been selected. (For example, whichmode's execution is set in the memory 7 of the NAS controller 5.) (S154)When the result of S154 is that either the first or second mode has beenselected, the NAS controller 5 hides the i-node of the overlap files,adds the i-node for a metadata aggregate file X (S155), and returns anaccess-approved reply (S157).

When the result of S154 is that the third mode has been selected, theNAS controller 5 adds the i-node of a generated raw-file image (i-nodefor a physical address image) (S156), and returns an access-approvedreply (S157).

Thus, a determination as to whether or not to hide overlap files is madewhen a file-mount request is received. Therefore, when the NAScontroller 5 receives a read command afterwards, overlap files can behidden from the backup server 101 even when it is not possible todetermine if this read command is a read command for backup, or anordinary read command from the information processing device 1.

FIG. 21B shows an example of the processing flow carried out when theNAS controller 5 receives a file read command from the backup server101.

When the received file read command is from a backup server that doesnot have access rights (S161: NO), the NAS controller 5 returns a replysignifying that access is denied (S162).

When the received file read command is from a backup server that doeshave access rights (S161: YES), the NAS controller 5 determines which ofthe first through the third mode has been selected (S163).

When the result of S163 is that the first mode has been selected, andthe NAS controller 5 carries out a read in accordance with the file readcommand, if access to a difference file(BNF) is required (S164: YES),the NAS controller 5 restores the old file targeted for read based onthis difference file(BNF), and sends the restored old file to the backupserver 101 (S166). Conversely, if access to a difference file(BNF) isnot required (S164: NO), the NAS controller 5 reads out theread-targeted file, and sends the read file to the backup server 101(S166).

When the result of S163 is that the second mode has been selected, theNAS controller 5 sends the difference file(BNF), which was read out inaccordance with the file read command, to the backup server 101 (S166).

When the result of S163 is that the third mode has been selected, theNAS controller 5 creates a physical address image file representing aphysical address image (S167), and sends this physical address imagefile to the backup server 101 (S166).

As described hereinabove, the NAS controller 5 can carry out backupusing a method that corresponds to the mode, which has been selected.

Embodiment 4

A fourth embodiment of the present invention will be explainedhereinbelow.

FIG. 22 shows an overview of processing carried out by a fourthembodiment of the present invention.

This fourth embodiment is an example of when the first embodiment of thepresent invention is applied to ILM (Information Lifecycle Management).

That is, in the first embodiment, the detection of files that are eithercompletely or partially overlapped can be carried out in a shorterperiod of time than when the above-mentioned brute-force method is used.When carrying out operations for managing file copies or versions, thereis a high likelihood that these files are important. In this fourthembodiment, important data is identified, and data identified as beingimportant is backed up without hesitation to an area with a higherreliability ranking.

For example, the NAS controller 5 can determine if a completely orpartially overlap file is an important file, and can either migrate orback up this file to an area, which has a high reliability ranking. Morespecifically, for example, when files that overlap one another eithercompletely or partially are detected, the NAS controller 5 will back upto a secured high reliability area one of the files in the case of filesthat are completely overlapped, and both of the files in the case offiles that are partially overlapped. Thus, even when data is lost fromareas that are not highly reliable due to malfunctions and the like,since important data is protected in a high reliability area, the riskof losing important data can be reduced. Furthermore, here, a “highreliability area” can be a storage area with a higher reliabilityranking than the storage area where the pre-migration file was stored,or it can be a storage area secured in advance as the storage area withthe highest reliability ranking.

Further, for example, when the source file or a file that has beenbacked up once is updated, the NAS controller reflects this in thebackup destination as well. Thus, even when data is lost from areas thatare not highly reliable due to malfunctions and the like, for example,the most recent file can be recovered by a systems administrator or auser with access rights accessing the relevant high reliability area.

Further, for example, the NAS controller 5 can save an update log ofimportant data to this high reliability area by managing this area as aWORM area (Write Once, Read Many area).

An overview of an example of a processing flow carried out by thisfourth embodiment will be explained below by referring to FIG. 22.

For example, as shown in FIG. 22, it is supposed that folder X is inLU0, folder Y is in LU1, and folder Z is in LU3 inside the storagedevice system 2. It is supposed that file A and file B are in folder X.It is also supposed that a reliability ranking of “2” is allocated toLU0 and LU1, and a higher reliability ranking of “1” is allocated toLU3.

In this case, for example, when the NAS controller 5 copies file A offolder X to folder Y, it uses reliability comparison table 55 to searchfor a LU that has a higher reliability ranking than LU0, in which folderX resides, and copies file A of folder X to folder Z in LU3, which waslocated as a result of the search. Then, the NAS controller 5 storesfile A itself of folder X, and the file-metadata 601 comprising thereference location information denoting the location of this file A, infolder Z. The NAS controller 5 also associates the file-metadata 603comprising the reference location information denoting the location offile A in folder Y, to the file A of folder Z (for example, itintegrates this metadata into file A).

Further, for example, when the NAS controller 5 updates file B in folderX under a different filename, it copies both the old file B and theupdate file B′ to folder Z. The NAS controller 5 also associates thefile-metadata 605 comprising the reference location information denotingthe location of file B in folder X, to the file B stored in folder Z(for example, it integrates this metadata into file B), and associatesthe file-metadata 607 comprising the reference location informationdenoting the location of file B′, to the file B′ stored in folder Z (forexample, it integrates this metadata into file B).

Further, for example, when the NAS controller 5 updates file A of folderX, which is the backup source, to file A′, it also reflects this updatein folder Z, the backup destination. More specifically, for example, asshown in the bottom portion of FIG. 22, the NAS controller 5 deletes oneof the file-metadata 601, 603 of file A, and associates thefile-metadata 609 comprising the reference location information ofupdate file A′ in backup source folder X, to the update file A′ storedin folder Z (for example, it integrates this metadata into update fileA′).

FIG. 23 is an example showing a more detailed overview of the processingflow shown in FIG. 22.

For example, when S69 of FIG. 11 is NO, if the old file has not beenbacked up (S201: NO), the NAS controller 5 carries out the processing ofS202 and subsequent steps. The NAS Controller 5 can determine whether ornot data has been backed up, for example, whether or not the samefile-metadata as the file-metadata of the data related to an old file(the above-mentioned second data or third data) has been associated to afile in a high reliability area, by referencing and checking the storagemanagement table 51.

The NAS controller 5 writes the first data to a high reliability area(S202), and adds an entry (either all or part of the file-metadata) ofthe first data written to the high reliability area to the storagemanagement table 51 (S203). The NAS controller 5 also writes the data ofthe old file of this first data (the above-mentioned second data orthird data) to a high reliability area (S204), and adds an entry of thedata of the old file written to the high reliability area to the storagemanagement table 51 (S205). In addition, the NAS controller 5 writes theentries added in S203 and S205 to a high reliability area (S212).

When S69 of FIG. 11 is NO, if the data has been backed up (S201: YES),the NAS controller 5 writes the first data to a high reliability area(S206), and updates the entry (the entry corresponding to the firstdata) in the storage management table 51 (S207). Thereafter, theabove-mentioned S212 is carried out.

When S69 of FIG. 11 is YES, and the first data (the write-targeted file)and an overlap file have not been backed up (S201: NO), the NAScontroller 5 writes the first data to a high reliability area (S209),and adds an entry for this first data and an overlap either second dataor third data (the original file, in other words, a completelyoverlapped old file) to the storage management table 51 (S210). Then,the NAS controller 5 adds an entry for the first data to the storagemanagement table 51(S211), and carries out S212.

When S69 of FIG. 11 is YES, and the first data (the write-targeted file)and an overlap file have been backed up (S201: YES), the NAS controller5 carries out the above-mentioned S211 and S212 without carrying outS209 and S211.

In this fourth embodiment, an old file and a file, which is eithercompletely or partially overlapped, can be backed up without hesitationin a LU with a high reliability ranking.

A number of preferred embodiments have been explained hereinabove, butthese embodiments are examples for explaining the present invention, andthe purport is not to restrict the scope of the present invention tothese embodiments alone. The present invention can be implemented in avariety of other aspects as well.

For example, as shown in FIG. 24, the functions of the NAS controller 5can be incorporated into the disk controller 23, and the NAS controller5 need not be provided. More specifically, for example, the processingcapable of being carried out by the CPU 11 of the NAS controller 5 canbe carried out by the CPU 25 of the disk controller 23.

For example, more than one physical storage device 45 and/or 46 can bemounted in the base chassis 21 as well. Further, a plurality of types ofphysical storage devices 45, 46 can coexist in the respective expansionchassis 23.

Also, for example, a flag signifying that a file is an overlap file, andthe reference location of the file-metadata of the file that overlaps itcan also be recorded in the file-metadata registered in the storagemanagement table 51. This makes it possible to retrieve information asto which files overlap which other files by referencing the storagemanagement table 51. Further, when one of the two files that overlapeach other is deleted, the file-metadata of this one file can bedeleted, and the file-metadata of the other file can be updated.Furthermore, for example, it is considered desirable to make combineduse of a system, which utilizes an overlap file list 403 in order tofacilitate the retrieval of three or more overlap files.

Also, for example, if there are up to two overlap files, operation willcoincide with the object, but when there are three or more overlaps,there will be cases when a portion of these is unnecessary. As explainedabove, since the overlapped parts are shared, the pressure on a storagearea (consumption) is small, but ill affects from a decline in retrievalefficiency can be expected. For this reason, it is desirable to deleteunnecessary files. Accordingly, for example, the CPU 11 of the NAScontroller 5 can monitor whether or not the number of files that overlapone another (hereinafter, number of overlaps) has reached apredetermined number, and when it is determined that this predeterminednumber has been reached, it can notify this fact to the informationprocessing device 1 into which the respective files are written. Sincethe CPU 11 of the NAS controller 5 can recognize the informationprocessing device 1 into which a file is written, it can collectivelycommunicate path names and other such file-metadata of other overlapfiles by sending a message to this information processing device 1regarding write operations that result in the number of overlaps beingmore than the predetermined number, and can urge the user of theinformation processing device 1 to delete an updated file (for example,a copied file). In addition, for example, by associating the ID of aninformation processing device 1 and its mailing address, and storingthese in the memory 7 of the NAS controller 5, when the number ofoverlaps reaches a predetermined number, the CPU 11 can automaticallysend an e-mail disclosing to the owner(s) of the respective files (theinformation processing device 1 and/or user) that the number of overlapshas reached a predetermined number, and can urge that an unnecessaryfile be deleted.

Also, for example, reliability rankings can be allocated in units otherthan LU units (for example, volume units or block units).

Further, for example, the reliability of a storage area can bedetermined using a method other than the method for referencing areliability ranking. For example, the reliability level can also bedetermined on the basis of that RAID level and/or the type of storagedevice (for example, FC or SAS).

Also, for example, a determination as to whether or not an overlap fileexists, for example, can be carried out by a CPU executing a prescribedcomputer program, or it can be carried out by a hardware circuit (forexample, a data controller 14).

Also, for example, when the reliability rankings of a first LU in whicha first overlap file is stored, and a second LU in which a secondoverlap file is stored are the same, the CPU 11 can release the areas inwhich overlap data resides from the LU that has less free area.

1. A storage control system, comprising: overlap retrieval means forretrieving overlap files, which are stored in at least one storage areaof a plurality of storage areas, and which overlap one another; andstorage control means for storing data of at least one overlapped partof said retrieved overlap files in a storage area having reliabilitygreater than that of the storage area in which the data of theoverlapped part is stored.
 2. The storage control system according toclaim 1, wherein a plurality of files are stored in said plurality ofstorage areas, and said overlap retrieval means retrieves said overlapfiles from among a number of files, which is less than the number ofsaid stored files.
 3. The storage control system according to claim 2,comprising: means for reading a file from at least one storage area; andfile marking means for marking a read file each time a file is read out,and controlling the number of marked files to a number, which is lessthan the number of said stored files, wherein said overlap retrievalmeans retrieves a file, which overlaps a certain file, from among aplurality of files that have been marked.
 4. The storage control systemaccording to claim 3, wherein said overlap retrieval means determines,sequentially from the most recently marked file, whether or not a filefrom among said marked plurality of files overlaps said certain file. 5.The storage control system according to claim 3, wherein, when saidoverlap file cannot be found among said marked plurality of files, saidoverlap retrieval means retrieves, from among one or more files forwhich either the entire or a part of the filename, and/or the file sizematches that of said certain file, a file, which overlaps said certainfile.
 6. The storage control system according to claim 1, furthercomprising: a reliability storage region capable of storing reliabilityinformation related to the reliability of each of a plurality of storageareas, wherein, when two files completely overlap one another, saidstorage control means determines, based on said reliability information,which file is in a storage area having high reliability, clears thelocation of the file, which is in a low-reliability storage area, andleaves the file in the high-reliability storage area.
 7. The storagecontrol system according to claim 1, further comprising: a reliabilitystorage region capable of storing reliability information related to thereliability of each of a plurality of storage areas, wherein, when pre-and post-update files partially overlap one another, said storagecontrol means, based on said reliability information, stores thepost-update file in a storage area that is more reliable than thestorage area in which the old file is stored, generates a differencefile for the pre- and post-update files, stores said generateddifference file in at least one storage area, and clears the locationwhere at least data of the overlapped parts of said old file reside. 8.The storage control system according to claim 1, further comprising: logfile updating means for writing information related to said retrievedoverlap files to a prescribed log file, wherein said overlap retrievalmeans retrieves said overlap files based on the information recorded insaid log file.
 9. The storage control system according to claim 1,wherein said storage control system is connected to a separate storagecontrol system so as to enable communications, and said storage controlmeans, by transferring all the files, which reside in a primary storagearea of said plurality of storage areas, to said separate storagecontrol system, copies said all the files to a secondary storage areaaccessible by said separate storage control system, and thereafter, whena certain file of said primary storage area is updated, transfers atleast the file metadata of the post-update file to said separate storagecontrol system.
 10. The storage control system according to claim 1,wherein said storage control system connects, so as to enablecommunications, to a backup device for acquiring a file stored in atleast one storage area, and backing up the file in a backup storagearea, and hides said retrieved overlap file from said backup device. 11.The storage control system according to claim 10, wherein said storagecontrol means generates a metadata aggregate file in which is recorded alarge number of file metadata corresponding to a respective large numberof files stored in said plurality of storage areas, stores saidgenerated metadata aggregate file in at least one storage area, andsends said stored metadata aggregate file to said backup device, therebyenabling restoration based on the file metadata recorded in saidmetadata aggregate file.
 12. The storage control system according toclaim 10, wherein said storage control means creates a physical addressimage file of at least one physical address image from said plurality ofstorage areas, and sends said created physical address image file tosaid backup device.
 13. The storage control system according to claim 1,wherein said storage control means backs up data of at least oneoverlapped part of said retrieved overlap files in a storage area havingreliability greater than that of the storage area in which the data ofthe overlapped part is stored.
 14. The storage control system accordingto claim 12, wherein, when a backup source file is updated after saidbackup, said storage control means reflects the results of the update inthe backup destination.
 15. The storage control system according toclaim 1, comprising: a threshold value storage region for storing athreshold value for the number of files, which are overlapped; and meansfor prompting a user to delete an unnecessary overlap file when thenumber of said retrieved overlap files becomes greater than saidthreshold value.
 16. A storage control system, comprising: overlapretrieval means for retrieving overlap files, which overlap one another,from among a number of files that is less than the number of filesstored in a plurality of storage areas; and controlling means forcarrying out prescribed processing for said retrieved overlap files. 17.A storage control method, comprising the steps of: retrieving overlapfiles, which are stored in at least one storage area of a plurality ofstorage areas, and which overlap one another; and storing data of atleast one overlapped part of said retrieved overlap files in a storagearea having reliability that is greater than that of the storage area inwhich the data of the overlapped part is stored.
 18. A storage controlmethod, comprising the steps of: retrieving overlap files, which overlapone another, from among a number of files that is less than the numberof files stored in a plurality of storage areas; and carrying outprescribed processing for said retrieved overlap files.
 19. A recordingmedium recording a computer program for causing a computer to retrieveoverlap files, which are stored in at least one storage area of aplurality of storage areas and which overlap one another, and to storedata of at least one overlapped part of said retrieved overlap files ina storage area having reliability that is greater than that of thestorage area in which the data of this overlapped part is stored.
 20. Arecording medium recording a computer program for causing a computer toretrieve overlap files, which overlap one another, from among a numberof files that is less than the number of files stored in a plurality ofstorage areas, and to carry out prescribed processing for said retrievedoverlap files.
 21. A storage control system, comprising: at least onestorage region; and at least one processor, wherein said at least oneprocessor reads a file from at least one storage device of a pluralityof storage devices in which a large number of files are stored, and eachtime a file is read out, marks the read file on said storage region, andcontrols the number of marked files to a number, which is less than thenumber of files stored in said plurality of storage device, retrieves afile, which overlaps a certain file, from among a plurality of filesthat have been marked, and stores data of at least one overlapped partof said retrieved overlap file in a storage device having reliabilitythat is greater than that of the storage device in which the data ofthis overlapped part is stored.